Method for producing an electrical heating device

ABSTRACT

A method for producing an electrical heating device with the steps of preparing a sleeve from a first material that has a first strength; arranging an electrical heating element in the sleeve; arranging of a filler material in the sleeve, so that parts of the electrical heating element carrying current are electrically isolated from the sleeve and the position of the electrical heating element in the sleeve is fixed, and at least section-wise compression of the sleeve, of the electrical heating element is arranged in sections of the sleeve that are compressed, and of the filler material arranged in sections of the sleeve that are compressed, wherein, before the completion of the at least section-wise compression of the sleeve, in sections to be compressed, a tubular section is arranged that is made from a second material that has a second strength higher than the first strength.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. 102018 109 306.3, filed on Apr. 19, 2018. The entirety of theaforementioned application is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

Electrical heating devices that have a sleeve with an electrical heatingelement arranged therein, whose parts carrying current are electricallyisolated from the sleeve, are a standard mechanism for the electricalheating of objects and/or media.

For many actual embodiments of such electrical heating devices, thereis, on one hand, the desire for the highest possible compression, inorder to guarantee the best possible heat conduction from the electricalheating device to the sleeve that is brought into contact with theobject or medium, while, simultaneously, the applicable compression mustbe limited, at least locally, for example, because other,pressure-sensitive elements, e.g., electronic components, are arrangedin the sleeve at some positions or because deformation caused by toomuch compression is not desired. This is taken into account bycompressing the sleeve to different degrees in different sections.

However, up to now the implementation of this approach in productionprocessing has proven not to be very reliable. In other electricalheating cartridges, there are production problems in that the strengthof the jacket material is not strong enough, for example, when a sleevemade from high-purity titanium is desired for medical applications.

Therefore, the problem of the invention is to disclose a method forproducing an electrical heating device, especially a heating cartridgeor a tubular heating body, that is improved especially with respect toits processing reliability.

This problem is solved by a method with the features of claim 1.Advantageous refinements of the method are the subject matter of thedependent claims.

BRIEF SUMMARY OF THE INVENTION

The method according to the invention for producing an electricalheating device has the steps of:

Preparation of a sleeve made from a first material that has a firststrength,

Arrangement of an electrical heating element in the sleeve,

Arrangement of a filler material in the sleeve, so that parts of theelectrical heating element carrying current are electrically isolatedfrom the sleeve and the position of the electrical heating element inthe sleeve is fixed, and

At least section-wise compression of the sleeve, of the electricalheating element arranged in sections of the sleeve that are compressed,and of the filler material arranged in sections of the sleeve that arecompressed.

It is preferable to the invention that, before the completion of the atleast section-wise compression of the sleeve, in sections to becompressed, a tubular section is arranged that is made from a secondmaterial that has a second strength that is higher than the firststrength.

In this way, the compression of the electrical heating device can beachieved with high precision and with process-reliable, highlyreproducible results.

This applies especially to electrical heating devices with areas thatare compressed to different degrees, because the area in which a givencompression is achieved can be defined locally in this way and acontrolled graduation of different degrees of compression can beimplemented. In addition, the annular clamping force with thecompression is assured by the additional tubular section made from amaterial with higher strength.

At this point it should be explicitly noted that the step of the atleast section-wise compression is naturally also realized if the entireelectrical heating device is simultaneously compressed.

The electrical heating element can here be, for example, a resistancewire wound on a coil body, especially a ceramic coil form, aself-supporting resistance wire, or also an embedded and positionedheating wire coil.

The filler material is usually an electrically isolating material withthe highest possible heat conductivity. In particular, it could bemagnesium oxide granulate.

The arrangement of this filler material in the sleeve can suggest, inparticular, the filling of an insulating powder, insulating granular, orother insulating parts.

According to one especially preferred embodiment of the method, thematerial from which the sleeve is made is copper, aluminum, titanium, orbrass, so that a sleeve made from copper, aluminum, titanium, or brassis prepared. All of these materials have in common that they haverelatively good heat conductivity, but not very high strength.

The sleeve that is preferably constructed as a tube that is closed onone side is preferably prepared in that, during manufacturing, it issubjected to cutting processes from a solid blank, deep-drawingprocesses from a metal sheet, or multiple die press processes.

The preferred material for the tubular sections to be arranged insections to be compressed is a steel, especially a stainless steel, thatis, a high-strength material.

In one preferred embodiment of the invention, it is provided that thearrangement of the tubular sections in the sections to be compressed isrealized for at least one tubular section such that it is pushed ontothe sleeve so that it surrounds the section to be compressed in theradial direction. This is associated not only with especially simple,precise positioning, but also enables a high-precision localizedapplication of force in the compression process, especially through theuse of a compression tool that applies force, at least at the start ofthe compression process, mainly on the pushed-on tubular section.

According to a preferred refinement of this embodiment of the method, itis provided that the compression is performed so that after thecompression, the pushed-on tubular section is aligned with sections ofthe sleeve on which no tubular section is pushed on.

However, it is also possible that the tubular section is pushed into thesleeve. This is provided, in particular, when the strength of the sleeveis too low to achieve the required annular clamping force or when ahomogeneous surface of the electrical heating device is required.

It is especially preferred when the possibility for creating preciselydefined, non-compressed or weakly compressed areas is used so that atleast one electronic component, especially a sensor, a fuse, and/or aswitch, is arranged in the sleeve. This is preferably realized in thatthe electronic component is arranged together with the electricalheating element in the sleeve, that is, in particular, as apreconfigured assembly.

Therefore, because a tubular section is arranged on the sleeve so thatit projects past the sleeve, in particular, past an end side of thesleeve, in particular, the possibility is created to produce theelectrical heating device with a closed area with defined properties.For example, in this way, an undesired flow of heat in the directiontoward the connections of the electrical heating device can be largelyprevented. In particular, it is possible that another tube thatconcentrically extends the sleeve is arranged in the area of the tubularsection projecting past the sleeve.

It can be advantageous to rework the bottom of the sleeve after thecompression process, especially so that a flat end surface is produced,which can be realized, for example, by a metal-cutting process on thebottom. Simultaneously, however, it is to be noted that due to themethod according to the invention, for an adapted selection of thedegree of compression of the respective areas, in many cases, adeformation of the end face during the compression process can beavoided, so that such a reworking step becomes unnecessary.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe preferred invention, will be better understood when read inconjunction with the appended drawings. For the purpose of illustratingthe invention, there are shown in the drawings embodiments which arepresently preferred. It should be understood, however, that theinvention is not limited to the precise arrangements andinstrumentalities shown. In the drawings:

FIG. 1a is a side perspective view of prepared components of a firstpreferred embodiment of an electrical heating device in accordance withthe present invention;

FIG. 1b is a cross-sectional view of the assembled prepared componentsof FIG. 1a before the compression process;

FIG. 1c is a cross-sectional view of the electrical heating deviceproduced from the components from FIG. 1a after the compression process;

FIG. 2 is a cross-sectional view of a second preferred embodiment of anelectrical heating device that can be produced with the preferred methodafter the compression process;

FIG. 3 is a cross-sectional view of a third preferred embodiment of anelectrical heating device that can be produced with the preferred methodafter the compression process;

FIG. 4a is a cross-sectional view of a fourth preferred embodiment of anelectrical heating device that can be produced with the method beforethe compression process;

FIG. 4b is a cross-sectional view of the heating device from FIG. 4aafter the compression process;

FIG. 5a is a cross-sectional view of a fifth preferred embodiment of anelectrical heating device that can be produced with the method beforethe compression process;

FIG. 5b is a cross-sectional view of the heating device from FIG. 5aafter the compression process;

FIG. 6 is a cross-sectional view of a sixth preferred embodiment of anelectrical heating device that can be produced with the method after thecompression process;

FIG. 7a is a cross-sectional view of a seventh preferred embodiment ofan electrical heating device that can be produced with the method beforethe compression process; and

FIG. 7b is a cross-sectional view of the heating device from FIG. 7aafter the compression process.

DETAILED DESCRIPTION OF THE INVENTION

If arrows are drawn in figures that still show non-compressed electricalheating devices, these arrows indicate the direction of the compressionof the system or method.

FIG. 1a shows the partially preconfigured components of an electricalheating device 100 prepared for performing the additional processingsteps in accordance with a first preferred embodiment. This figureshows, in particular, the electrical heating element 110 constructed ascoil body 112 wound with a resistance wire 111, and the sleeve 130 madefrom copper and the tubular section 140 made from stainless steel.Naturally, copper and stainless steel have their own strength values,and the strength of stainless steel is higher than that of copper.

The electrical heating element 110 is also preconfigured here to theextent that an electronic component 150, namely here a temperaturesensor, is arranged on the coil body on the end side and a connection toconnecting wires 160 has already been produced.

In the representation of the electrical heating device 100 before theprocessing step of the at least section-wise compression in FIG. 1b ,the electrical heating element 110 has been arranged in the sleeve 130and the filler material 120 has been arranged in the form of magnesiumoxide powder also in the sleeve 130, so that parts of the electricalheating element 110 carrying current, namely the resistance wire 111,are electrically isolated from the sleeve 130 and the position of theelectrical heating element 110 in the sleeve 130 is fixed.

By means of the processing step of the at least section-wise compressionof the electrical heating device 100, this arrangement can then betransformed into the shape shown in FIG. 1c . In particular, only acompression of the area of the tubular section 140 made from stainlesssteel was performed here, so that it has a compressed section 101 and anon-compressed section 102, in which the electronic component 150 isarranged. Here, the compression was performed so that the tubularsection 140 is now aligned with the profile of the sleeve 130 in thenon-compressed section 102 of the electrical heating device 100.

FIG. 2 shows a second preferred embodiment of an electrical heatingdevice 200 that can be produced with the method with compressed section201, non-compressed sections 202,203, electrical heating element 210with resistance wire 211 and wound coil body 212, filler material 220,sleeve 230, tubular section 240, electronic component 250, andconnecting wires 260 after the at least section-wise compressionprocess.

The difference with the electrical heating device 100 of the firstpreferred embodiment relative to the second preferred electrical heatingdevice 200 is that the tubular section 240 does not include theconnection-side end area of the electrical heating device 200 and thesleeve 230, so that a second non-compressed area 203 is created. Thiscan be useful, for example, for many kinds of electrical connectionsbetween connecting wires 260 and the electrical heating element 210and/or the electronic component 250.

FIG. 3 shows a third preferred embodiment of an electrical heatingdevice 200 that can be produced with the method with compressed section301, non-compressed sections 302,303, electrical heating element 310with resistance wire 311 and wound coil body 312, filler material 320,sleeve 330, tubular section 340, electronic component 350, andconnecting wires 360 after the at least section-wise compression.

Differently than for the electrical heating device 200 of the secondpreferred embodiment, for the electrical heating device 300 of the thirdpreferred embodiment, the tubular section 340 projects past theconnection-side end area of the sleeve 330, wherein an additional tube370, in this embodiment, again a stainless steel tube, is arranged inthe area of the tubular section 340 projecting past the sleeve 330,wherein this tube concentrically extends the sleeve 330. In this way,the heat transport to the connection side can be reduced.

FIGS. 4a and 4b show a fourth preferred embodiment of an electricalheating device 400 that can be produced with the method with compressedsection 401, non-compressed section 402, electrical heating element 410with resistance wire 411 and wound coil body 412, filler material 420,sleeve 430, tubular section 440, electronic component 450, andconnecting wires 460 before and after the at least section-wisecompression, respectively.

The difference with the electrical heating device 100 of the firstpreferred embodiment relative to the fourth preferred electrical heatingdevice 400 consists in that the tubular section 440 is part of anothersleeve 441 surrounding the sleeve 430, wherein both sleeves 430, 441each have a larger cross section in the area to be compressed before thecompression process than in the area not to be compressed.

FIGS. 5a and 5b show a fifth preferred embodiment of an electricalheating device 500 that can be produced with the method with compressedsection 501, non-compressed section 502, electrical heating element 510with resistance wire 511 and wound coil body 512, filler material 520,sleeve 530, tubular section 540, and connecting wires 560 before andafter the at least section-wise compression, respectively.

The electrical heating device 500 of the fifth preferred embodiment isrelated to the third preferred electrical heating device 300 in that,like in that third preferred electrical heating device 300, the tubularsection 540 projects past the sleeve 530 in the connection-sidedirection. Differently than in the third preferred electrical heatingdevice 300, however, in the fifth preferred embodiment according toFIGS. 5a and 5b , no other tube is arranged in this area. Anotherdifference with the electrical heating device 300 of the third preferredembodiment is that the sleeve 530 of the fifth preferred electricalheating device 500 has a reinforced bottom 531 with significantlyincreased wall thickness. This is preferred especially if anydeformation of this bottom during the compression process is to becompensated for, in particular, by metal-cutting rework processes, e.g.,by dressing. In addition, there is also no electronic component.

FIG. 6 shows a sixth preferred embodiment of an electrical heatingdevice 600 that can be produced with the method with compressed section601, electrical heating element 610 with resistance wire 611 and woundcoil body 612, filler material 620, sleeve 630, tubular section 640, andconnecting wires 660 after the compression process.

The electrical heating device 600 of the sixth preferred embodiment isstructurally similar to the electrical heating device 500 of the fifthpreferred embodiment, but differently than in the third preferredembodiment, there is a thermocouple element 650 in the sixth preferredembodiment on the bottom side and the tubular section 640 completelyhouses the sleeve 630.

FIGS. 7a and 7b show a seventh preferred embodiment of an electricalheating device 700 that can be produced with the method with compressedsection 701, non-compressed section 702, electrical heating element 710with resistance wire 711 and wound coil body 712, filler material 720,sleeve 730, tubular section 740, electronic component 750 and connectingwires 760 before and after the at least section-wise compressionprocess, respectively.

The difference with the electrical heating device 100 of the firstpreferred embodiment according to FIGS. 1a to 1c consists in that thetubular section 740 of the seventh preferred embodiment is pushed intoand not onto the sleeve 730.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

LIST OF REFERENCE SYMBOLS

-   100,200,300,400,500, 600,700 Electrical heating device-   101,201,301,401,501, 601,701 Compressed section-   102,202,302,303,402, 403,502,602 Non-compressed section-   110,210,310,410,510, 610,710 Electrical heating element-   111,211,311,411,511, 611,711 Resistance wire-   112,212,312,412,512, 612,712 Coil body-   120,220,320,420,520, 620,720 Filler material-   130,230,330,430,530, 630,730 Sleeve-   140,240,340,440,540, 640,740 Tubular section-   150,250,350,450,550, 750 Electronic component-   370 Tube-   441 Sleeve-   531 Bottom-   650 Thermocouple element

What is claimed is:
 1. A method for producing an electrical heatingdevice comprising the steps of: preparing a sleeve from a first materialthat has a first strength, arranging an electrical heating element inthe sleeve, arranging a filler material in the sleeve, so that parts ofthe electrical heating element carrying current are electricallyisolated from the sleeve and a position of the electrical heatingelement in the sleeve is fixed, arranging a tubular section radiallyupon or within at least one section of the sleeve, the tubular sectionbeing made from a second material that has a second strength that isgreater than the first strength; and compressing the at least onesection of the sleeve having the tubular section, including theelectrical heating element and the filler material arranged therein,whereby the at least one section of the sleeve having the tubularsection is compressed to a greater degree than other sections of thesleeve without the tubular section, resulting in greater compaction ofthe at least one section of the sleeve having the tubular sectionrelative to the other sections of the sleeve without the tubularsection.
 2. The method according to claim 1, wherein the preparing stepcomprises preparing the sleeve from copper, aluminum, titanium, orbrass.
 3. The method according to claim 1, wherein the tubular sectionis made from steel and is arranged for sections to be compressed.
 4. Themethod according to claim 3, wherein the tubular section is made fromstainless steel.
 5. The method according to claim 1, wherein the step ofarranging a tubular section comprises pushing the tubular section ontothe sleeve.
 6. The method according to claim 5, wherein the compressingstep results in aligning the pushed-on tubular section with sections ofthe sleeve on which no tubular section is pushed on.
 7. The methodaccording to claim 1, wherein the step of arranging a tubular sectioncomprises pushing the tubular section into the sleeve.
 8. The methodaccording to claim 1, further comprising the step of arranging whereinat least one electronic component in the sleeve.
 9. The method accordingto claim 8, wherein the step of arranging at least one electroniccomponent comprises arranging the at least one electronic componenttogether with the electrical heating element in the sleeve.
 10. Themethod according to claim 8, wherein the at least one electroniccomponent comprises a sensor, a fuse, and/or a switch.
 11. The methodaccording to claim 1, wherein the step of arranging the tubular sectioncomprises projecting a portion of the tubular section past the sleeve.12. The method according to claim 11, further comprising the step ofpositioning an additional tube in the portion of the tubular sectionprojecting past the sleeve, thereby concentrically extending the sleeve.